You should provide additional information about your setup. Which steps did you follow to install SageMath? Which installation of latex are you referring to? (you did install latex in the virtual box?)
BTW, is there any reason why you use Virtualbox? You could give a try to the windows binaries. They are much more up to date than the virtual box.
Feel like I downloaded half the Internet..." That's probably part of your problem right there. Without more details, we can't possibly know exactly what you did, how your computer is configured, or what the problem is. But usually throwing more downloads at the problem without understanding what you're doing is only likely to break more things and make the problem exponentially more difficult to untangle (for example you wrote "I reinstalled Python"; but Sage includes its own Python interpreter and should have nothing to do with other Pythons on your system). Did you install Sage using the executable installer? If so there's no need for Virtualbox in the first place. And sage-8.6.tar.gz is just the source code.
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